As image forming apparatuses such as printers, copiers, facsimile machines, multifunction peripherals provided with their functions, etc., there are known those that are provided with a photosensitive drum as one example of an electrophotographic photosensitive body, a charging device which electrostatically charges the surface of the photosensitive drum, and a cleaning blade which is arranged in contact with the surface of the photosensitive drum and which removes the toner and additive that remain on the surface of the photosensitive drum.
The photosensitive drum is composed of, for example, a drum pipe made of metal which serves as a support body and a photosensitive layer which is formed on the surface of the drum pipe. As photosensitive drums, there are proposed, for example, those that use amorphous silicon for the photosensitive layer and that has the surface of the drum pipe coarsened (e.g., Patent Documents 1 and 2).
In the photosensitive drum described in Patent Document 1, a plurality of spherical vestigial dents are formed on the surface of the drum pipe such that, over a reference length of 2.5 mm on the surface of the photosensitive drum, the ten-point average roughness Rz is in the range of 0.72 [μm] or more but 1.25 [μm] or less. In this way, adhesion of toner at the time of remaining toner cleaning is suppressed, and the scar resistance of the surface of the photosensitive drum is improved.
On the other hand, in the photosensitive drum of Patent Document 2, linear grooves in a triangular shape are formed on the surface of the photosensitive drum in the circumferential direction so that the surface condition of the photosensitive drum is such that the center-line arithmetic average roughness Ra is in the range of 0.08 [μm] to 0.12 [μm] and the ten-point average roughness Rz is in the range of 0.45 [μm] to 0.75 [μm]. In this way, the rotation torque of the photosensitive drum is reduced.